ESDU 94044

Excrescence drag levels on aircraft.

ESDU 94044 is based on manufacturer's estimated values for a large number of aircraft as manufactured and provides a guide to standards that have been achieved and a method to obtain a first approximate estimate. In most cases a datum drag parameter is presented at the troposphere and a Mach number of 0.8; a correction factor to other altitudes and speeds whose derivation is included is based on a detailed study of the variation of excrescence drag with Reynolds and Mach numbers. The drag parameter is plotted against wetted area for complete airframes but, for a more detailed estimate, values for some categories of excrescence are also given graphically. They are: surface and control imperfections, air-data systems, lights and beacons, antennas, static discharge wicks, auxiliary power unit, and features required for rain dispersal, for ventilation/cooling, for air-conditioning and for fuel systems. Some information is included on the extent that 'clean-up' has proved possible on several aircraft.